Numerous microorganisms, for example, those of the genera Arthrobacter, Brevibacterium, Microbacterium, Protaminobacter, Bacillus, Norcardia, Streptomyces, and especially Mycobacterium, are capable of degrading zoosterols and phytosterols to carbon dioxide and water. During the degradation, 4-androstene-3,17-dione and 1,4-androstadiene-3,17-dione are formed as intermediates.
The degradation of the sterols to avoid further degradation of the thus-formed 4-androstene-3,17-dione or 1,4-androstadiene-3,17-dione is accomplished by using inhibiting additives or mutated microorganisms. See DOS's (German Unexamined Laid-Open Applications) 1,543,269 and 1,593,327, and U.S. Pat. No. 3,684,657.